Study On Relative Slip Between Wires And Damage Identification Of Stayed Cables

The parallel stayed cable structure,such as parallel steel strands and parallel wire cables,is the main load-bearing structure in the cable-stayed bridge system.Its structural performance and health have a significant impact on the safety,reliability and durability of cable-stayed bridges.Common injuries to stayed cables include cracking,pits,aging shedding,wire breakage,wire rust,wire wear and interlayer relative slip.The interlayer relative slip between wires causes a reduction in the local bending stiffness of the cable,which causing damage to the mechanical properties of the parallel cable.In this paper,parallel cable structures are taken as research objects.The interlayer relative slip damage between parallel cable layers is studied by three parts,including the theoretical derivation of mechanical mechanism analysis,numerical simulation calculation of finite element modeling analysis,and damage identification and parameter identification based on different methods.The development law of interlayer relative slip between parallel cable layers and the effective feasible damage identification methods for interlayer slip damage are obtained.Firstly,this paper takes the steel strand in the stayed cable as the research object,and establishes the space thin rod model of the steel wire based on the spatial spiral coordinate system.The spatial static equilibrium equations of steel strands are derived.The influence of the change of section properties of steel strands on the mechanical properties of the strands under tensile load is analyzed.Considering the frictional contact effect between steel stranded steel wires,the refined finite element model of steel strands was established by ANSYS finite element software.By reasonably selecting the contact surface parameters of the face-to-face contact pair and based on the enhanced Lagrangian multiplier method,the stress distribution law of the stayed cable and the relative contact slip between the steel wires are obtained.Secondly,the interlayer relative slip between layers of parallel cable is equivalent to the relative slip between layers of the frictional laminated beam.According to the theory of "stratified slip",the law of slip development between parallel layers is derived.Based on the Transfer Matrix method,a numerical method for calculating the longitudinal slip length of parallel cables is proposed.The calculation program of the proposed method is compiled by MATLAB,and the calculation results of this program are compared with the simulation calculation results of ANSYS.The comparison results verify the correctness of the proposed method.The influencing factors of the interlayer relative slip damage of the stayed cables are also analyzed.Thirdly,the cable interlayer slip damage identification process based on the eigenpair sensitivity method is proposed.By introducing the Tikhonov regularization method and the L-curve regularization parameter optimal selection method,the parameters of the discrete system structure are solved iteratively.The results of different examples show that the eigenpair sensitivity damage identification method can identify the variation of stiffness and damping parameters of the structure,and the accuracy and noise robustness are better.Combined with the law of stiffness variation before and after the relative slip between the parallel cable wires,the proposed method can accurately locate the damage of the interlayer relative slip unit of the parallel cable and identify the damage of the slip state.Fourthly,a new bird mating optimization algorithm based on the Boltzmann selection(BBMO)is proposed.By comparing the optimization results with five existing group intelligent algorithms on multiple different types of benchmark test functions,it is verified that the BBMO algorithm has relatively better optimization performance in the optimization problem calculation.Fifthly,a parameter identification method for the stayed cable system with damper based on the BBMO algorithm is proposed here.The parameter identification calculation is based on the actual test frequency of the parallel cable of the Binjiang cable-stayed bridge.The results show that the parameter identification method based on BBMO algorithm can identify multiple parameters such as cable force,bending stiffness,effective cable length and linear density simultaneously.Sixthly,the BBMO algorithm proposed in this paper is used to identify the interlayer slip damage of the stayed cable system with damper.Considering with the stiffness loss caused by the relative slip between the parallel cable layers,the frequency and modal data before and after the slip damage are combined with the BBMO optimization algorithm to identify the interlayer slip damage of the stayed cable.The results show that the interlayer slip damage identification method based on BBMO algorithm can accurately locate and identify the local stiffness damage caused by interlayer slip damage of the stayed cable,and the method has good noise robustness.